1. Field of the Invention
The present invention relates to normally opened solenoid valves.
2. Description of the Related Art
Conventionally known techniques concerning normally opened solenoid valves include one described in JP-A-2002-347597.
In a normally opened solenoid valve described in JP-A-2002-347597, its valve body includes: a shaft part; and a tip part provided at an extremity of the shaft part and serving as a valve closing body, and the shaft part and the tip part are formed in one piece by injection molding using a resin material.
The tip part has: a conical portion provided adjacent to the shaft part; a columnar portion provided continuously with the conical portion; and a valve part that is provided at an extremity of the columnar portion, and is provided, at its end portion, with an abutting surface abutted against a valve seat.
The shaft part is inserted into a through hole formed in a fixed core, and the above-described valve body is slid by driving of a movable core.
In the above-described normally opened solenoid valve, the valve body is formed in one piece using a resin material, thus obtaining advantages that a reduction in weight of the valve body is enabled and a responsiveness of an opening/closing operation is improved.
Actually, in JP-A-2002-347597 described above, the conical portion provided in the tip part of the valve body is formed into a simple conical shape. Therefore, the volume of the valve body is increased in the tip part of the valve body, which might cause a so-called “sink mark (shrink mark)” in the valve part at the time of molding, and might cause a reduction in shape accuracy of the valve part.
As measures to be taken to suppress occurrence of such a sink mark, the tip part of the valve body may be conceivably reduced in volume. However, a simple reduction in the volume of the tip part of the valve body might lead to a reduction in strength of the tip part.